Semiconductor devices are devices that utilize semiconductor materials, which are solid materials that exhibit an electrical conductivity intermediate between that of a conductor and that of an insulator. Semiconductor devices include, for example, diodes (e.g., light emitting diodes (LEDs)), photovoltaic devices, sensors, solid state lasers, and integrated circuits (e.g., memory modules and microprocessors). Photovoltaic devices are semiconductor devices that convert photons (e.g., light) into electricity. For example, solar panels include photovoltaic devices that convert sunlight (i.e., photons originating from the sun) into electricity. Due to the ever-increasing demand for renewable energy sources, the market for photovoltaic devices has experienced an average annual growth rate of about twenty-five percent (25%) over the previous decade.
Manufacturing processes for thin films of semiconductor materials include electroplating techniques, vapor deposition, flash evaporation, and evaporation from binary compounds, spray pyrolysis, and radiofrequency or ion beam sputtering of polycrystalline materials. In addition, semiconductor materials, such as chalcopyrite materials, may be formed by decomposing one or more so-called “single source precursors” (SSPs), which are organometallic substances (e.g., molecules, complexes, etc.) that include all of the atomic elements, in the appropriate stoichiometric ratios, necessary to form a chalcopyrite material.
Extensive research and development has resulted in semiconductor devices that are cheaper and more efficient. A majority of semiconductor devices that are commercially available include photodiodes formed in silicon substrates. The performance of such silicon-based photovoltaic devices, is however, inherently limited by physical and chemical properties of silicon. New photovoltaic devices have been created that are based on light-absorbing materials (which may be either organic or inorganic) other than silicon. The number of non-silicon-based photovoltaic devices has steadily increased over the previous two (2) decades and currently accounts for over ten percent (10%) of the solar energy market. Non-silicon photovoltaic devices are expected to eventually replace a large portion of the market for silicon-based photovoltaic devices and to expand the solar energy market due to their material properties and efficient power generating ability. In order for solar power to be economically competitive with alternative fossil fuel power sources at their current prices, photovoltaic devices based on photoactive materials other than silicon must be improved and further developed.
Materials other than silicon that can be employed in semiconductor devices include, for example, germanium (Ge), chalcopyrites (e.g., CuInS2, CuGaS2, and CuInSe2), chalcogenides [Cu(InxGa1-x)(SeyS1-y)2], cadmium telluride (CdTe), gallium arsenide (GaAs), organic polymers (e.g., polyphenylene vinylene, copper phthalocyanine, fullerenes), and light absorbing dyes (e.g., ruthenium-centered metallorganic dyes). Photovoltaic devices based on such materials demonstrate promise of being less expensive than silicon-based devices, while delivering photon conversion efficiencies comparable to those exhibited by silicon-based devices. Furthermore, some non-silicon photovoltaic devices are capable of capturing a broader range of electromagnetic radiation than silicon-based devices, and as such, may be more efficient in producing electrical power from solar energy than are silicon-based devices.
Non-silicon semiconductor devices may include thin films of semiconductor materials, which films may include polycrystalline materials or nanoparticles. The thin films of semiconductor materials may be formed on flexible substrates such as polyethylene terephthalate (such as that sold under the tradename MYLAR®), which allows for a broad range of new configurations, designs, and applications for semiconductor devices that were previously unavailable to silicon-based devices. Furthermore, thin film designs may use less than one percent (1%) of the raw materials used in conventional silicon-based devices, and therefore, may cost much less than silicon-based devices in terms of basic raw materials.
Conventional semiconductor devices, such as LEDs, include lanthanide-based materials. By way of example, the lanthanide-based materials function as the phosphor in the LEDs. However, lanthanide-based materials are expensive due to a high demand for, but limited supply of, these materials. It would be desirable to provide a lower cost alternative to lanthanide-based materials in semiconductor devices, such as LEDs.